1. Field of the Invention
The present invention relates to a system that uses a wireless microphone to transfer audio to an image pickup apparatus, a recording apparatus, or an audio mixer, and to a wireless microphone, an audio transmitting apparatus, an audio receiving apparatus, an image pickup apparatus, a recording apparatus, and an audio mixer that include such a system.
2. Description of the Related Art
In recent years, when news broadcasts and the like are filmed on location, it has become increasingly common to record audio transferred using wireless microphones. FIGS. 1A and 1B show the appearance of two examples of a wireless microphone. FIG. 1A shows wireless microphone transmitters (hereinafter simply “transmitters”) as apparatuses for transmitting audio. Each of the transmitters 81, 82 fundamentally includes a microphone (in the case of the transmitter 82, a pin microphone, not shown, that is connected by a cable) and a modulating/transmitting unit that transmits radio waves that have been modulated using an audio signal from the microphone. The transmitter 81 is a hand microphone-type transmitter that is held by hand. Conversely, the transmitter 82 is a transmitter that is attached to a waist belt or the like.
FIG. 1B shows a wireless microphone receiver (hereinafter simply “receiver”) as the apparatus for receiving the audio. The receiver 83 fundamentally includes a receiving/demodulating unit that receives radio waves transmitted from the transmitter 81 or transmitter 82 and demodulates the audio signal and an output terminal that outputs the demodulated audio signal to the outside.
FIGS. 2A and 2B are diagrams showing examples of an audio transfer system that uses the transmitter 81 and the receiver 83 shown in FIGS. 1A and 1B to record audio during ENG (Electronic News Gathering). In the example in FIG. 2A, the transmitter 81 is used by a reporter conducting an interview. The receiver 83 is attached to a slot provided on a camcorder 91 (i.e., a camcorder integrated with a recorder such as a VTR or optical disk apparatus) or is connected to the camcorder 91 by a cable. The audio signal inputted from the receiver 83 into the camcorder 91 is recorded by the camcorder 91 together with the images picked up by the camcorder 91.
In the example in FIG. 2B, the transmitter 81 is used by a reporter and the receiver 83 is connected by a cable to an audio mixer 92. The audio signal inputted from the receiver 83 into the audio mixer 92 is mixed or switched inside the audio mixer 92 and the audio signal outputted from the audio mixer 92 is recorded by a VTR or audio recorder or camcorder, not shown.
In the past, for a wireless microphone such as the examples shown in FIGS. 1A and 1B, a circuit that emits a tone signal of a predetermined frequency outside the audible spectrum is provided inside the transmitter, such tone signal is superimposed on an audio signal and transmitted from the transmitter, and a circuit that detects this tone signal is provided inside the receiver, so that information can be transmitted as described below, for example.                The receiver identifies the radio waves from the transmitter and distinguishes the waves from interference        The receiver is informed of a drop in the voltage of a battery inside the transmitter and an indicator on the receiver is lit        
In the past, to reduce in size of this kind of wireless microphone, the transmitter and the receiver have been provided with only a minimal number of operation buttons for carrying out setting operations of the respective devices.
Moreover, for this type of wireless microphone, Japanese Unexamined Patent Application Publication No. 2007-36735 has disclosed a technology where the receiver detects unused frequencies in the radio waves based on the reception level of the radio waves and outputs information showing the detected unused frequencies to a camcorder or audio mixer (such information being displayed by the camcorder or audio mixer) so that the operator of the camcorder or audio mixer can check which frequencies are unused and set the frequency to be used by the wireless microphone.